c=3, N=2 超共形场论的Z2 Orbifold-Prime模型

讨论了二维环面上中心荷c=3, N=2 的超共形场论. 特别给出该理论的配分函数. 进一步,为了产生新的模型,回顾了一般的orbifold方法. 然后构造了模不变的Z2 Orbifold-Prime模型.     

Local versus non-local charges in integrable field theories

We contrast the two types of charge, local and non-local, which appear in integrable (1+1)-dimensional integrable quantum field theories based on Lie algebras. This is the wider setting for the new work which we describe, on local conserved quantities in principal chiral models.     

Planar Yang-Mills theory: Hamiltonian,regulators and mass gap

We carry out the Hamiltonian analysis of non-Abelian gauge theories in (2+1) dimensions in a gauge-invariant matrix parametrization of the fields. A detailed discussion of regularization issues and the construction of the renormalized Laplace operator on the configuration space, which is proportional to the kinetic energy, are given. The origin of the mass gap is analyzed and the lowest eigenstates of the kinetic energy are explicitly obtained; these have zero charge and exhibit a mass gap. The nature of the corrections due to the potential energy, the possibility of an improved perturbation theory and a Schrödinger-like equation for the states are also discussed.     

Dimensional reduction by legendre transformation generates off-shell supersymmetric Yang-Mills theories

A new technique of dimensional reduction by Legendre transformation to derive off-shell formulations of extended supersymmetric theories is presented. The method starts from an on-shell theory in a higher dimension and retains a dependence of the fields upon one of the higher dimensions, thus allowing for a central charge in the four-dimensional supersymmetry algebra. The “hamiltonian density” of the theory plays the role of the lagrangian in one less dimension, while the equations of motion serve as constraints for the lower dimensional theory. These constraints guarantee supersymmetric and central charge invariances of the action. The technique is applied to derive off-shell formulations of the supersymmetric Yang-Mills theories.     

Conserved charges and thermodynamics of the spinning Gödel black hole

We compute the mass, angular momenta, and charge of the G?del-type rotating black hole solution to five-dimensional minimal supergravity. A generalized Smarr formula is derived, and the first law of thermodynamics is verified. The computation rests on a new approach to conserved charges in gauge theories that allows for their computation at finite radius.     

刃型位错高斯光束的Riemann-Silberstein涡旋通过双焦透镜的聚焦特性

基于时间平均复标量场的零值点,推导出寄居于高斯光束中的刃型位错线形成的Riemann-Silberstein (RS)涡旋通过双焦透镜传输时的复标量场。详细研究了刃型位错高斯光束形成的RS涡旋通过双焦透镜的聚焦特性,分析了传输距离和双焦透镜在x方向的焦距对RS涡旋的影响。研究发现RS涡旋通过双焦透镜后会出现RS涡旋的移动、新产生一对含有相反拓扑电荷的RS涡旋、两个含有相反拓扑电荷的RS涡旋逐渐靠近至湮灭,但是,在整个聚焦传输变化过程中,RS涡旋的总拓扑电荷守恒。特别地,当RS涡旋通过理想透镜时,复标量场中始终只有4个位于x轴上的RS涡旋。随着传输距离增加,这4个RS涡旋先逐渐靠近原点(0, 0),又逐渐远离原点(0, 0),但每个RS涡旋的拓扑电荷一直保持不变,因此,总拓扑电荷守恒。     

均匀电荷密度下的磁绝缘理论研究

在平行板磁绝缘传输线中均匀电荷密度下,分别对压力平衡下的修正层流模型和非压力平衡和非层流模型进行了求解,比较了两种理论模型下的结果。分析表明：相对于非层流模型而言,层流模型因未考虑径向速度,其电荷密度偏低,阳极电场、阳极磁场及阳极电流都偏大。此外,粒子模拟结果显示非层流模型具有更高的精度。最后,对压力平衡条件、均匀电荷密度下的层流以及非层流模型,从平行板理论推广到一般构型。     

Intrinsic weak link originating from tilt in contacts between dx2-y2 wave superconductors

x²-y² wave superconductors, which form a contact at a tilt angle. The contact is a weak link or a Josephson junction, with properties determined by the misalignment angle. Complementing existing theories that discuss the influence of d_x2-y2 symmetry on the charge transfer across junctions, the ideas presented provide insights into the origin of the junction formed in such configurations. The mechanism discussed is of relevance for the understanding of the electronic properties of grain boundaries in superconductors, including the angular dependence of the critical current density. Received: 5 July 1996/Accepted: 7 January 1997     

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With the uniform charge density in the magnetically insulated transmission line (MITL) of parallel plate, a laminar flow model with pressure balance and a new model without the assumption of laminar flow and pressure balance are solved analytically, respectively. The results of laminar flow model and non-laminar flow model are compared. It is shown that the charge density is smaller and electric field, magnetic field on anode is bigger in laminar flow model as without radial velocity of electrons. Then, the result of particle-in-cell simulation is compared for the two theories and shows that the accuracy of non-laminar model is higher than laminar model. Finally, the pressure balance equation and two models of laminar and non-laminar with the uniform charge density have been promoted to coaxial MITL and cone MITL.     

Zero temperature phase diagram of the ferromagnetic Kondo lattice

We study numerically the one-dimensional ferromagnetic Kondo lattice, a model widely used to describe nickel and manganese perovskites. Due to the competition between double and super-exchange, we find a region where the formation of magnetic islands induces a charge-ordered state. This ordering is present even in the absence of any inter-site Coulomb repulsion and presents an insulating gap associated to the charge structure. We study the metal–insulator transition induced by a magnetic field which removes simultaneously both charge and spin orderings. This new mechanism should be taken into account in theories of charge ordering involving spin degrees of freedom.     

Some remarks on nonlocal field theory and space-time quantization

From the point of view that the charge and mass of an electron is of dynamical origin and quantization of charge in units ofe is related to the space-time quantization as developed in an earlier paper, we here show that it is possible to consider that the internal space within the elementary domain of the quantized space-time world is not governed by Lorentz invariance. This helps us to develop a consistent theory of nonlocal fields for extended particles where the infinite mass degeneracy is avoided. Moreover, this ensures the convergence of nonlocal field theories and suggests that massless particles like photons and neutrinos, though they may be taken to be of extended structure, will appear only as point particles in the physical world. In this picture, Lorentz invariance appears to be a consequence of the distribution of matter and energy in the Universe, and this may be taken to be another interpretation of Mach's principle.     

New Light on Infrared Problems: Sectors,Statistics, Symmetries and Spectrum

A new approach to the analysis of the physical state space of a theory is presented within the general setting of local quantum physics. It also covers theories with long range forces, such as quantum electrodynamics. Making use of the notion of charge class, an extension of the concept of superselection sector, infrared problems are avoided by restricting the states to observables localized in a light cone. The charge structure of a theory can be explored in a systematic manner. The present analysis focuses on simple charges, thus including the electric charge. It is shown that any such charge has a conjugate charge. There is a meaningful concept of statistics: the corresponding charge classes are either of Bose or of Fermi type. The family of simple charge classes is in one-to-one correspondence with the irreducible unitary representations of a compact Abelian group. Moreover, there is a meaningful definition of covariant charge classes. Any such class determines a continuous unitary representation of the Poincaré group or its covering group satisfying the relativistic spectrum condition. The resulting particle aspects are also briefly discussed.     

Quantum Charges and Spacetime Topology: The Emergence of New Superselection Sectors

A new form of superselection sectors of topological origin is developed. By that it is meant a new investigation that includes several extensions of the traditional framework of Doplicher, Haag and Roberts in local quantum theories. At first we generalize the notion of representations of nets of C*–algebras, then we provide a brand new view on selection criteria by adopting one with a strong topological flavour. We prove that it is coherent with the older point of view, hence a clue to a genuine extension. In this light, we extend Roberts’ cohomological analysis to the case where 1–cocycles bear non-trivial unitary representations of the fundamental group of the spacetime, equivalently of its Cauchy surface in the case of global hyperbolicity. A crucial tool is a notion of group von Neumann algebras generated by the 1–cocycles evaluated on loops over fixed regions. One proves that these group von Neumann algebras are localized at the bounded region where loops start and end and to be factorial of finite type I. All that amounts to a new invariant, in a topological sense, which can be defined as the dimension of the factor. We prove that any 1–cocycle can be factorized into a part that contains only the charge content and another where only the topological information is stored. This second part much resembles what in literature is known as geometric phases. Indeed, by the very geometrical origin of the 1–cocycles that we discuss in the paper, they are essential tools in the theory of net bundles, and the topological part is related to their holonomy content. At the end we prove the existence of net representations. Dedicated to Klaus Fredenhagen on the occasion of his sixtieth birthday     

Effect of electrode material on sealing wax thermo-electret charge

Thermo-electrets of sealing wax have been prepared using different metal electrodes: tin, aluminium, nickel, copper, lead and zinc (Series A) and pairs of metallic — tin and non-metallicmica (Series B) keeping other preparative parameters to be the same in each series. Surface charge has been measured on anode side of each thermo-electret. Surface charge characteristics have been discussed in the light of the results obtained in earlier studies on sealing wax thermo-electrets by the authors and existing views on the origin of charges. These results suggest that origin of homocharge in thermo-electrets is due to injection of charge carriers supplied by the electrodes into the dielectric surface and freezing in near the surface and getting trapped in the surface levels. The origin of heterocharge is due to inhomogeneous distribution of charge carriers originating in the bulk on account of their trapping.     

Asymptotic freedom: An approach to strong interactions

The discovery of asymptotic freedom has opened up the possibility of extracting new sorts of detailed, dynamical consequences from a strongly interacting quantum field theory. The necessary tools - perturbation theory, the renormalization group, gauge theories, and the operator product expansion - are not new. To anyone familiar with these field theoretic approaches to strong interactions, the novel feature is a simple fact: there is a unique class of theories in which “the origin is an ultraviolet fixed point”. But the consequences are so exciting that it seemed appropriate to review these ideas as they reflect on each other. Many important applications of the renormalization group and the operator product expansion to hadronic physics are omitted; the emphasis here is on recent work based on asymptotically free field theories. No doubt, there are some developments so recent that they are not treated in this article.The discussion of the basic results concerning short distance behavior is informal, but, hopefully, accurate and complete. The specific applications are treated in varying detail.     

c-Theorem for disordered systems

We find an analog of Zamolodchikov's c-theorem for disordered two-dimensional non-interacting systems in their supersymmetric field theory representation. We show that the energy momentum tensor of such field theories must be a part of a supermultiplet, and that a new parameter b can be introduced with the help of that multiplet. b flows along the renormalization group trajectories much like the central charge for unitary two-dimensional field theories. While it has not been established if this flow is irreversible, that is, if b always flows down to lower values, it does so for all the cases worked out so far. b gives a new way to label different conformal field theories for disordered systems whose central charge is always 0. b turns out to be related to the central extension of a certain algebra, a generalization of the Virasoro algebra, which we show may be present at the critical points of these theories. b is also related to the finite size corrections of the physical free energy of disordered systems. We discuss possible applications by computing b for two-dimensional Dirac fermions with random gauge potential, in other words, for U(1∣1) Kac-Moody algebra.     

Electric field control of magnetism in multiferroic heterostructures

We review the recent developments in the electric field control of magnetism in multiferroic heterostructures, which consist of heterogeneous materials systems where a magnetoelectric coupling is engineered between magnetic and ferroelectric components. The magnetoelectric coupling in these composite systems is interfacial in origin, and can arise from elastic strain, charge, and exchange bias interactions, with different characteristic responses and functionalities. Moreover, charge transport phenomena in multiferroic heterostructures, where both magnetic and ferroelectric order parameters are used to control charge transport, suggest new possibilities to control the conduction paths of the electron spin, with potential for device applications.     

Simulation of charge reversal in salty environments: Giant overcharging?

We have performed MD simulations of a highly charged colloid in a solution of 3:1 and additional 1:1 salt. The dependency of the colloid's inverted charge on the concentration of the additional 1:1 salt has been studied. Most theories predict, that the inverted charge increases when the concentration of monovalent salt grows, up to what is called giant overcharging, while experiments and simulational studies observe the opposite. Our simulations agree with the experimental findings and shed light onto the weaknesses of the theories.     

On the role of the interface charge in non-ideal metal–semiconductor contacts

The bias dependent interface charge is considered as the origin of the observed non-ideality in current–voltage and capacitance–voltage characteristics. Using the simplified model for the interface electronic structure based on defects interacting with the continuum of interface states, the microscopic origin of empirical parameters describing the bias dependent interface charge function is investigated. The results show that in non-ideal metal–semiconductor contacts the interface charge function depends on the interface disorder parameter, density of defects, barrier pinning parameter and the effective gap center. The theoretical predictions are tested against several sets of published experimental data on bias dependent ideality factor and excess capacitance in various metal–semicoductor systems.     

Shielding of a moving test charge in a turbulent plasma

The far-field potential of a moving test charge in a turbulent collisionless plasma is calculated. Our results differ considerably from previous test charge theories in nonturbulent plasmas.